Lens and the manufacture thereof



I 1942- G. JAECKEL LENS AND THE MANUFACTURE THEREOF 3 Sheets-Sheet 1 Original Filed Sept. 8, 1939 Feb. 3, 1942. ECKEL 2,272,119

LENS AND THE MANUFACTURE THEREOF Original FiIed Sept 8, 1939 3 Sheets-Sheet 2 crane data-r52,

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Feb. 3, 1942. G, JAECKEL 2,272,119

LENS AND THE MANUFACTURE THEREOF Original Fil'ed Sept. 8,' 1939 3- Sheets-Sheet 5 MW QR seams J/YEOYEL,

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Patented Feb. 3, 1942 ICE LENS AND THE MANUFACTURE THEREOF Georg Jaeckel, Berlin-Lichterfelde,

assignor to the flrm Sendlinger werke G. m. b. H., Beriin-Zehlendorf,

Original application salami..- s, 1939, semi No. 294,031, now Patent No. 2,246,098, dated June 17, 1941. Divided an tember 8, 1939, Serial No. 294,032.

a many March 20, 1936 Claims.

The invention relates to lenses and to the manufacture thereof. Y

This application is a division of my application 8. N. 294,031, filed September 8, 1939, executed concurrently herewith for improvements in Lenses and the manufacture thereof, and which issued as Patent No. 2,246,098, June 1'7, 1941.

A primary object of the invention is to produce a stepped lens of the Fresnel type from pressed glass which is designed to prevent the loss of light passing through the lens.

Further objects and advantages of the invention will appear more fully from the, following description, particularly when taken in conjunction with the accompanying drawings, which form a part thereof.

In the drawings:

Fig. 1 shows the procedure ordinarily used in manufacturing a stepped lens;

Fig. 2 shows, in perspective and partly in cross section, a lens produced according to the invention:

' Fig. 3 shows, in perspective and partly in cross section, a blank used for making the lens disclosed in Fig. 2;

Fig. 4 shows similarly a modified form of blank;

Fig. 5 shows diagrammatically the light, path in the ordinary stepped lens produced in the manner shown in Fig. 1;

Fig. 6 shows atically the path of light a lens embodying one form of the invention; v

Fix. 7 shows in cross section a mold for making a lens according to the invention; and

Fig. 8 shows a modified form of lens embodying theinvention with its method. of production.

Ontisehe Glas: Germany d this application Sep- The usual type of stepped lens 2 as shown in Fig. lhas a series of steps such as AB, CD,, E5, GE, 13 connected by surfaces BC, DE, GF and 'm. The'lower surface may have any desired shape but is usually a smooth convex curve. The

lens is produced by pressing in a mold l, the

plunger 8 of' which has steps LM, NO, PQ, RS

, and TU connected by surfaces MN, OP, RQ and TS. Obviously in the production of a lens in this manner the step-connecting surfaces, such as BC, must be either parallel to the axis W of the lens 2, this line V'W also indicating the direction of movement of the plunger die 6 in shaping the glass, or must be outwardly inclined, that is, conversing toward a point on the side of the convex surface of the lens. Such surfaces could not be undercut since then it would be impossible to remove the plunger die I after the'pressing The disadvantage of a lens of this type is shown in Fig. 5. Assuming that light comesfrom the focus M of the lens, some of this light will strike the step-connecting surfaces, such as the surface GF. .Thislsindicated by the arrow 6 in Fig. 5. This light will be refracted outwardlyand will be lost. Obviously the greater the relative aperture of the lens the greater will be the amount of light so'lost, since a greater proportion of the light will strike the step-connecting surfaces. d

According to the invention this loss of light is avoidedby a method which makes the step-conthe molding'the plunger. die could not be re-- necting surfaces radialto the main focus of the lens. As shown in Fig. 6, for example, step-conmeeting surfaces be, etc, of, and ih of lens 8 all point towards or are radial to the same point m which is the lens focus. Obviously, no light will strike these surfaces so that they are optically inactive, and therefore no light will be lost through outward refraction from the step-connecting sur faces. In the case of a circular lens, these surfaces-will, ofcourse, represent conical surfaces of which the focus m is the apex. The surfaces must, of course, be inwardly inclined.

The production of such a lens by the method shown in Fig. 1 would be'impossible, since after moved from the lens. In order to produce a lens, therefore, the method shown in Figs. 3 and '7 is utilized.

Assuming that the-lens II is to have the form shown in Fig. 2, in which the step-connecting surfaces are radial to the focus. 1121, a block is molded in the form shown in Fig. 3, the block there being shown in perspective, and partly in section, for producing a circular stepped lens. The outer points a; and In of the lens of Fig. 2 are shown at the center of Fig. 3, dividing the same into two parts Ila and Nb, while the central plane in, 21, m of Fig. 2 is shown at theoute dent that steps gill, iihi, her, and (1181, are all A faced outwardly, that is to say, they are notundercut, and converge towards points on the side of the concave surface of the lens.

' The die plunger may be lifted after the pressing without dimmilty.

Q5 The two halves connected at In, m may be for v The step surfaces descend towards the outside of the body of .ing the successive points an, In, g2, ha, in, 762, b2,

02, d2, e2, $2, 112, an, ha, 112 is molded in the shape shown therein, having two parts Hi and I lid. .In this form it will be noted again that there are no undercut surfaces, and that the step-- connecting surfaces converge towards points on the side of the concave surface, so that the plunger may be easily removed after the pressing operation. The two parts we and "Id are then separated by breaking the portion a:, k2, and the surfaces is, :02, y: are brought together and fused,

producing a lens similar to that of Fig. 2.

While in Fig. 3 the breaking on line In; a1

produces lines of breakage on both the upper and lower surfaces-of the lens, the structure of Fi 4 requires breakage only through the connecting web a: which may then be ground off, or used to support the lens during further grinding.

Fig. 7 shows the mold for producing the lens of the type shown inFig. 6. The desired shape of lens blank is represented in Fig. 7 by the white space between the mold parts. The bottom mold section-is formed in two parts, I2, l4, l4, l6, l8

and l2, l4, 1'4, I1, 23, respectively, said parts being substantially symmetrical and separated along theline |2, l4. The surface l4, ll, l'4 has the shape of the convex side of the lens blank which is desired.

The plunger die is also produced in two parts a4,.2l, 26 and a4, 25, 26. These two parts are separated along the line a4, 28. The surface of the plunger corresponds to that desired for the inside or concave surface of the lens blank to be produced; v

It will be noted 'that surfaces II, II; and a4, 26 are straight, and that they are in a straight line in the mold of Fig, 'l. Surfaces l2, ll are secured together to produce the lower moldpart.

For the plunger die part, surfaces a4, 26. are secured to produce the plunger die.

By pressing glass with the mold bottom and plunger die shown in Fig. '7, a lens body is pro-- duced. This lens body is then broken along the line (la-I, and surfaces 1'4, 25 and 24, l 4 are joined together. The final lens body is substantially similar to that shown in Fig. 6 in its characteristics.

Fig. 8 shows the procedure for manufacturing a lens for ships lanterns, for example, of the annular type. Such lens is not formed as a surface of revolution about the central path of the light, but as a surface produced by the displacement of a closed outline of the shape shown either in a straight line or in a circle.

Such annular lenses can be produced in the manner shown in Fig. 8. The lens is produced in the two separate, identical parts shown in the figure, and divided therein by the line 16-11.

Obviously either the lower half or the upper half of the lens may be molded without difficulty, as

there are no' undercut steps during the molding.

The connecting portions H, 12, 13, 14 may be broken out after the parts are formed. The portions llle,- I0! are then connected along-the line I6-"ll, and the lens is completed.

While I have described herein some embodi that I do not intend to limit myself thereby ex-' cept within the scope of the appended claims.

I claim:

1. A method of forming a concave-convex lens with step surfaces on the concave side of the lens descending towards the center of the lens and step-connecting surfaces all converging towards at least one point spaced from the concave side of the lens, comprising molding a body in concave-convex form in two symmetrical parts centrally Joined with the step surfaces descendingtowardsthe outside of the body. dividing the body centrally, and connecting the outer parts of the body together to form the lens. Y

2. Amethodof making stepped lenses having inwardly facing step-connecting surfaces converging towards the focus of the lens, comprising simultaneously molding a body in two symmetrical lens parts centrallyjoined with said step; connecting surfaces facing outwardly, dividing said body centrally, and ioiningthe outer parts of the body together to form the lens. x

3. A methdd of forming a concave-convex lens with step surfaces on the concave side of the lens descending towards the center of the lens-and step-connecting surfaces all directed towards a common point spaced from the concave side of the lens, comprising molding a body in concavoconvex form in two symmetrical parts centrally 40 joined with the step-connecting surfaces converging towards the concave side of the body, dividing the body-central1y, and connecting the outer parts of the body together to form the lens.

4. A method of forming a concavo-convex lens with step surfaces on the concave side of the lens descending towards the center of the lens and step-connecting surfaces all directed towards a common point spaced from the concave side of the lens, comprising molding a body in concave-convex form in two symmetrical parts centrally :loined with the step surfaces descending towards the outside of the body, and the step onnecting surfaces converging towards points on the concave side of the body dividing the body centrally, and connecting the outer parts of the body together to form the lens.

5. A method of making concayo-convex stepped lenses having inwardly directed step connectin surfaces converging towards at least one point spaced from the concave side of the lens, com prising simultaneously molding two connected symmetrical lens parts with the step'connecting ...surfaces converging towards at least one point spaced from the concave side of the lens and the steps descending towards the outside of the said body. separating said parts, and connecting the outer portions thereof to form the lens.

GEORG JAECKEL.

ments of my invention, I wish it to be understood 4 

